1. Field of the Invention
The present invention generally relates to ink-jet printers and methods of controlling electronic systems which use such printers, and more particularly to a method and apparatus for recovering ink flow quality in an ink-jet type print head.
2. Related Technical Art
Ink-jet type printers are finding increasing use because of such advantages as low noise during printing, compact lightweight devices, and low power consumption.
However, when ink-jet printers remain in a non-operating or non-operational state or condition for an extended period of time, solvent evaporation and other effects cause the viscosity of any ink residing in the print head nozzles to increase. This results in inadequate ink discharge whenever printing resumes. Even if the increased viscosity does not cause improperly directed discharge of the ink, the amount of ink discharged may be less than normal, resulting in ink dots of differing diameters being output during printing and degrading print or output quality.
Some representative examples of techniques employed in the art in an attempt to solve these ink-jet printer related problems are disclosed in Japanese Published Patent application 61-56109 and U.S. Pat. No. 4,558,332. In both of theses patents, a method is used in which subsequent printing operations are first proceeded by detecting a prescribed period of non-operation or a time period over which discharge was interrupted and performing extra ink discharge, blank discharge, or other types of recovery.
However, as shown in these examples, printing typically has to be interrupted or the recovery process performed immediately prior to actual printing, which lengthens printing time and effectively slows down the printing speed. Also, if a printer user forgets to power down the printer mechanism, or the period of non-operation becomes extended through non-use, the amount of ink consumed as part of recovery processing unavoidably increases, which also increases power consumption and decreases efficiency. A further problem with the latter example is that, recovery is performed only prior to a subsequent printing operation even if a prescribed period of non-operation is exceeded, so that the ink viscosity in the nozzles increases even further, and recovering a desired ink discharge quality, which is the purpose of using a single recovery operation of a few discharge cycles, can not be achieved. That is, an extended period of non-operation causes the nozzles to become clogged while waiting for a recovery operation, and normal recovery is insufficient to recover the proper use of the ink-jet head.
As seen above, there are still problems in the art in trying to satisfy demands for high speed, high efficiency, and high reliability in ink-jet printers and printing mechanisms. What is needed is a new method and apparatus for solving these problems.